In the co-pending application of Edwin A. Link, Ser. No. 616,673 entitled "Method of Use and Electrical Equipment Utilizing Insulating Oil Consisting of a Saturated Hydrocarbon Oil", filed on Sept. 25, 1975, now U.S. Pat. No. 4,082,866 certain highly refined petroleum oil and mineral oils were disclosed which were considered sufficiently nonflammable to serve as insulating oil substitutes for polychlorinated byphenyls in electrical equipment. The essence of this invention was the avoidance of terminal olifenic bonds and significant advantages with respect to dealing with the problems associated with catastrophic failure in electrical apparatus. The insulating oil was additionally characterized as being of any average molecular weight between 500 and 700, having a fire point about 200.degree. C., and remaining liquid down to near 0.degree..
Within those boundary conditions, it has been found that considerable differences exist in the usefulness of various oils considered for this purpose. The most obvious of these was the difference in pour point associated with the degree of dewaxing performed on the base fluids from which the oil was produced. Also the flash and fire points of a hydrocarbon dielectric oil can be increased by selectively distilling the lower molecular weight components from the oil.
Having discovered these differences in the various oils, it was decided to determine the aggregate effect on the physical and electrical properties obtained by blending the various oils. The unanticipated effects of blending on these properties was explained as being the result of filling the voids between molecules in the various liquid blends with other molecules in the blend. In other words, it is believed that the dissimilar molecules fit together into a more compact higher density structure which produced the unanticipated improvements in the physical and chemical properties of these blends.